Pressure-type alarm device



Jan. 27, 1953 MENDES 2,626,585

PRESSURE-TYPE ALARM DEVICE Filed Dec. 15, 1950 IN V EN TOR. ABQAHAM P/ ZA ME NDES BY yw/l M 54 ATTORNEYS Patented Jan. 27, 1 953 UNITED STATE PRESSURE-TYPE ALARM DEVIC Abraham Piza Mendes, New York, N. Y. 7 Application December 15, 1950, Serial No. 200,893

3 Claims.

1 c My invention relates to improvements in alarm devices and has particular reference to an alarm device which will automatically emit a loud and prolonged Warning sound when the surrounding air temperature is raised beyond a predetermined limit. Such an alarm device is especially applicable for use as a fire alarm, and it may also be used to give warning of conditions conducive to theinitiation of combustion, as in places where grain and paint are stored. The device is intended to be used generally to indicate any undesirable elevation c-f temperature, as in the case of an overloaded motor or faultily-lubricated bearing, or malfunction of a cooling or refrigerating mechanism.

' r I am aware of several alarm devices in the prior art which utilize containers of compressed air or carbon dioxide to actuate a whistle or similar sound device. In these alarm devices, the containers are generally sealed, the seal being designed to melt at the temperature at which it is desired that the device operate, the compressed gas then escaping through the sound device to produce a warning noise. In order to operate a whistle or siren long enough and loud enough to give a warning that would be of practical value, a considerable quantity of gas must be available for a considerable length of time. The gas is therefore best stored in the container in a liquified state. However, the pressures developed by air and by carbon dioxide so stored, at normal room temperatures and more so at temperatures at which fire alarms are operated are so high that extremely strong and therefore heavy containers are required for the required quantity of gas.

Unless regulating means were introduced into the device it would be virtually inoperative because no ordinary whistle or siren'will operate throughout the range of pressures, from the maximum at opening to the minimum as the container empties. Further, as everyone knows who has used a carbon dioxide cartridge to inflate a life belt or charge a soft drink siphon charger, the cartridge empties in a moment so that the period, if any, during which such a prior art device as described would emit. a sound would be very brief. v

Because of the aforementioned considerations, 1'. utilize in my alarm devices substances which boil, under pressure of one atmosphere, at temperatures near that at which the alarm is intended to operate. Thus, the vapor pressur of these substances at all temperatures at which the deviceis to be used is low enough for the substance to be safely retained by a container having thin,

light walls.

The principal object of my invention is the provision of an alarm device which has a conev tainer for storing a substance which boils at or near the temperature at which it is desired that thedevice emit a warningsignal, together with sound-producing mean-s adapted to be operated by the gas emitted by the boiling substance.

Another object of the invention is the provision of any alarm vdeviceof thecharacter described in which'the sound-producingmeans is associated with a seal which normally. Seals off the container, so that the substance therein'can not evaporate, but which is adaptedto open automatically when the temperature risesto the operative level of the alarm device;

' Still another object, of the invention is the provision of an alarm device of the character described in which't'he substance in the'con-tainer has a vapor pressurewhich is moderate at all temperatures within the probable range of use of the device, below its boiling point, so that the container may be made with thin, light walls, affording economy in manufacture.

Other objects and advantages of the invention will be readily apparent in the course of the following specification when taken; in connection with-the accompanying drawings, inwhich;

Fig.- 1 is an elevational view of the'c-ontainer utilized in the alarmdevica witha sound producing unit connected to the mouth thereof;

Fig. 2 is an enlarged central vertical section of the sound-producing unit of Fig. 1, showing the closure means therefor;

Fig.3 is a horizontal section taken along lines 33,of Fig. 2; and, V

Fig.- 4, is a central vertical section showing another type of sound-producing unit connected to the mouth of the container, said unit having a modified closure means.

Referring in detail to the drawings and in particular to Fig. 1, I provide a hollow container l0 whose walls are made from a heat-conductive material, preferably metal. The container ID has a relatively highsurfacearea in proportion to its internal cubic volume, on the principle of a flash boiler, so that changes .in the surrounding air temperature are quickly and efiectively tively moderate pressure, as compared to compressed air or carbon dioxide when held in part in liquid phase at the same temperatures. For this reason, the container in may be made simple and economically, having thin walls and an internally-threaded neck I I for the reception of a seal and a sound-producing unit.

The container 10 is filled with a substance which has a boiling point not far below the temperature at which the alarmdevice is desired to emit its warning signal. For this purpose, I have found that such substances as methylene chloride, trichlorethylene, and several of the fluorinated hydrocarbon derivatives of the short 7 chain and small ring aliphatic series of organic compounds (known commercially as Freonsb possess the physical characteristics necessary for the successful operation of the alarm device in its several different applications. The Freon substances have boiling points ranging from l98.39 F.'to +199.0 F., so that they may be used to indicate the presence of excessive heat (as in a fire alarm) or to indicate the failure of refrigerating apparatus. In addition, these substances also possess the desirable characteristics of being non-flammable, non-toxic, non-explosive, extremely stable, and generally noncorrosive.

Although other substances may suggest themselves, it may be'noted that thefollowing substances are especially suitable since they boil at one atmosphere of pressure at temperatures ranging from 199 F. to 4l F. The boiling point of tetrachlorodifluoroethane (CC12F--CC12F) r Freon 112 is 199.0 F.; that of trichlorethylene (CHCl:CCl2) is 188.6 F.; that of trichlorotrifluoroethane (CC12F-CC1F2) or Freon ll3is ll'7.6 F.; that of trichloromonofluoromethane (CClsF) or Freon 11 is 743 F.; that of dichlorotetrafluoroethane or Freon 114 is 384 F.; that of dichlorodifluoromethane (CClzFz) or Freon12 is 21.6" F.; and that of monochlorodifiuoromethane (CHClFz) or Freon 22 is 41.4 F.

When the container is filled withsuch a substance, elevation of the surrounding air temperature causes the temperature of the substance to rise correspondingly due to the transmission of heat through the walls of the container Iii. When the temperature reaches the level at which it is desired thatthe device operate, the seal between the container and the sound device opens, as will be presently described. At this time the contained substance will be actively boiling, and because of the flash boiler construction of the container, will continue to supply a sufficient amount'of vapor to operate. the alarm to producea loud warning signal for anadequate length of time.

Fig. 2 illustrates one type of seal and soundproducing unit 20 which may be associated with the container II] in order to provide a complete alarm device.

The unit 20 comprises a cylindrical block 2! which bears external threading 22 for attachment respectively to the internally threaded neck H of container H at one end, and at the other end to a hollow whistle casing 23-whi'ch has anopen, internally threaded end 24. The block 2| has one or more bores or air passages 25 which permit gas from container .10 to pass into whistle casing 23 :an'dthence tothe'atmosphere through an aperturelfiyinwhistle casing 23. The aperture 26 is covered by the usual type of reed 21, which vibrates as the gas escapes through aperture 26, sounding a signal which lasts as long as the gas continues to flow.

The bores of block 2| are sealed liquidtight and gas-tight by a bi-metallic unit 28 which is secured to the outer surface of block 2| by any suitable means such as a screw 29. While the unit 28 may be of any type of bi-metallic thermostatic element, I prefer to use a conventional thermostatic circular disc which is shown in Fig. 3. Such devices have a critical temperature below which they are curved or dished in one direction-as shown in full line in Fig. 2, and above which they snap suddenly in an oppositely curved position as shown in broken line in Fig. 2.

The outer surface of the block 2 I may be shaped approximately to follow the curve of the disc 28 in its normal curved position. The block 2| may contain a circular recess 39 which surrounds the bores 25 and which contains an annular washer or resilient gasket 3 I. In the normal curved posi-- tion of the disc 28, the outer edge of said disc presses into said washer 2 I, providing atight seal over the bores 25. It is evident that the lower the surrounding temperature, the greater will be the pressure with which the disc 28 presses into the washer 3i.

Thermostats of the type described are marketed in various forms to operate at selected temperatures. A thermostat may be chosen to operate at a temperature at which the alarm device is desired to sound, which temperature is therefore higher than-the boiling point of the substance in the container Hi. When the surrounding air temperature reachesthe boiling point of the substance, said substance will begin to boil and to be converted to gas. When the temperature reaches the operative level of the thermostatic disc 28, the disc 23 snaps to its oppositely-curved position, permitting the gas to flow through the bores 25, to the interior-of the whistle casing 23, and past the reed 2?, out the apertureZfi. As the substance in the container continues toboil, gas continues to flow through the whistle-aperture 28 so that a lowland-prolonged warning signal is emitted until all of the substance in the container H) has boiled away.

Fig. l illustrates another embodiment of the sound-producing unit which comprises a hollow casing in which a whistle 36 a is slidably mounted. The casing 35 is open at both ends, one of said ends having external threading 37 for attachment to the internal threading i i of container Iii, and the-other end having an internal flange 42. The whistle 3B- is of the conventional type having an air-inlet opening 38, and a reed 39 positioned'adjacent an outlet opening 40 which is located centrally intermediate the ends of the whistle 36. The whistle also has a projecting peripheral flange At which slidablyabuts the inner surface of the casing-35 and is positioned to abut the internal flange 42 of casing 35. The solid closed end 33 of the whistle 35 extends slidably through the flange d2 of casing '35. A bar of-fusible metal 46 extending through a bore of the casing 35 and into a slot 46 in the solid closed end of the whistle 38, normally locks the whistleiifi in an inoperative sealed position shown in full line in Fig. 3. In this position, the outlet opening of the whistle 36 is located within the casing. 35 whose outer end is closedfoff by the solid closed end43 of the Whistle 36.

The metal bar 4.4 is made of a metal or alloy which melts ata temperature such as that ,pro-

duced by the approach of fire or by conditions conducive to the outbreak of fire, and the substance in the container is selected to have a boiling point close to or the same as the melting temperature of the bar M.

When the surrounding air temperature rises to the boiling point of the substance in the container II], the pressure of the gas generated within the container Ill urges the whistle 36 outwardly relative to the container H5. The rise in temperature causes the bar 44 to melt, releasing the whistle 36 and enabling the whistle to be slid outwardly by the pressure of said generated gas to its operative position shown in broken line in Fig. 4. In the aforementioned operative position, the outlet opening 40 of the whistle 36 is located externally of the casing 35, and the flange 4| is in contact with the flange 42, preventing further outward movement of the whistle 36. The gas generated in the container l0 may now pass freely through the inlet opening 38 and out of the outlet opening 40, producing a warning sound.

While preferred embodiments of my invention have been shown and described herein, it is obvious that numerous additions, changes, and omissions may be made in the invention without departing from the spirit and scope thereof.

I claim:

1. An alarm device comprising in combination a container having a large surface area in proportion to its cubic content and having heatpermeable walls, said container containing a liquid which boils at a selected temperature, a gas-operable sound device having a liquid-tight and gas-tight connection with said container and communicating with the interior of said container, and closure means normally held in an operative position in which it seals off the sound device from the passage of gas therethrough, said closure means having a heat-sensitive member which normally maintains said closure means in its operative position, said heat-sensitive member being responsive to a rise in the surrounding temperature to a selected level above the boiling point of said liquid, thereby moving closure means out of its operative position, whereby gas from the boiling liquid may flow through said sound device to produce a warning signal.

2. An alarm device comprising in combination a container having a large surface area in proportion to its cubic content and having heatpermeable walls, said container containing a liquid which boils at a selected temperature, a gasoperable sound device, a connecting member between said sound device and the interior of said container, said connecting member having a through-and-through air opening, and a bimetallic thermostatic element secured adjacent said air opening and having a normal curved shape in which it closes said opening to the passage of gas therethrough, said thermostatic element being adapted to snap to out of its normal curved shape and to an oppositely curved shape in which it uncovers said opening when the surrounding temperature rises to a selected level above the boiling point of said liquid.

3. An alarm device comprising in combination a container having a large surface area in proportion to its cubic content and having heatpermeable walls, said container containing a liquid which boils at a selected temperature, a gasoperable sound device, a hollow tube communicating with the interior of said container, said sound device comprising a whistle slidably mounted in said sound device, said whistle having an air inlet at its inner end and an outlet, said air inlet communicating with the interior of said container through said tube, said outlet being located intermediate the ends of said whistle, and a metal plug normally locking said whistle in a contained position in said tube in which the outer end of said whistle closes off the outer end of said tube, said metal plug having a melting point slightly higher than the boiling point of said liquid.

ABRAHAM PIZA MENDES.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,312,175 Hansen Aug. 5, 1919 2,034,179 Franklin Mar. 17, 1936 2,483,657 Messick Oct. 4, 1949 

